Speculation

Spidews are considered to be Heavy, Mountable units, whereas Marbits are small humanoid units with likely low stats, that fight better in tunnel situations. Because the counter-attack by Manpower the Temporary took place above ground, outside of the city,Erf-b1-p001 the Gobwin Knob forces likely had the tactical advantage over the marbits. Due to the extra squad of axemen (How many is a squad?), Manpower left himself open to ranged attack and was croaked. The death of a warlord signaled defeat for Gobwin knob, whose stacks would have lost significant leadership multipliers as well as the tactical ability to retreat. It is assumed that all of Manpower's forces were destroyed, because there was no living warlord to direct them to flee. Erf-b1-p044